Road building machines



Jan. 25, 1966 J. CURLETT ETAL 3,230,846

ROAD BUILDING MACHINES Filed May 15, 1961 2 Sheets-Sheet 2 /s'o w b F! 65 WKW United States Patent 3,230,846 ROAD BUILDING MACHINES JohnCurlett, Los Gates, and Raymond A. Gurnes, San Jose, Calif., assignorsto Gurries Manufacturing Co., San Jose, Calif., a corporation ofCalifornia Filed May 15, 1961, Ser. No. 110,087 7 Claims. (CI. 94-46)This invention relates to road building machines and more particularlyto an improved leveling control system which provides a three-pointsuspension of the tool-carrying main frame of a road building machinewith respect to its ground traction units. A

Road building machines are utilized to a great extent for suchoperations as scraping road beds and laying subbase, base, black top andconcrete for surfacing the scraped roadbed. Essentially, road buildingmachines comprise (1) a main frame for carrying appropriate roadbuilding tools such as strike-off'blades, conveyor screws and scrapers,(2) traction units for propelling the main frame forward or backward,and (3) frame supports for connecting the four corners of the main frameto the traction units. Since the traction units arein direct contactwith the ground where grade, cross grade and general surface conditionsare usually different from the road surface level to be constructed, andsince the road building tools are firmly fixed to the main frame,vertically adjustable supports are utilized to maintain the position ofthe main frame and thereby the road building tool at an accurate andpredetermined level reflecting a desired grade and cross gradeirrespective of the grade, cross grade and irregularities of the groundengaged by the traction unit. Of course, if the irregularities of theground are very great, the demands made upon the adjustable supports maybe somewhat reduced by utilizing angle blades mounted to the front ofthe main frame and maintained at the level of the working tool to cut apath over which the ground traction units may move.

The vertically adjustable main frame supports of the prior art includevertically positioned hydraulically operated rams connecting each cornerof the main frame to a traction unit. Heretofore, each hydraulic ram wascontrolled independently of the other hydraulic rams either manually byan operator or automatically by a level guide such as grade wires orgrade surfaces or a combination thereof disposed along the sides of theroad bed to be constructed. In this manner, each of the four corners ofthe main frame was kept at a fixed height with respect to the levelguide which controlled the degree of extension of the hydraulic ramsassociated with that corner.

Prior art road building machines, because of their four corner control,have certain inherent limitations with respect to their stability,versatility and etliciency. For example, it is always necessary toprovide for two guide levels, one along each side of the road, tocontrol the grade and cross grade of the tool-carrying main frame.Furthermore, four independently servo actuated corner supports attachedto the four corners of a rigid frame provide what may be termed a fourpoint suspension system. Since only three of the four corner supportscan operate at any one time to determine the plane of the main frame,one support is generally not supporting its corner. Of course, thatcorner of the main frame will be at the proper height due to the actionof the other three supports, but its support will not carry its portionof the weight of the frame when the ground is uneven and drops awaysince there can be no servo action as long as the main frame is in itsrequired plane. Consequently the full load of one side of the frame isthen carried by the single active support causing a doubling of the workpressure. This extra weight thrust upon the active support causes avariation 3,230,845 Patented Jan. 25, 1966 of compaction under thetraction unit to which it is connected and extra movement of the mainframe which must be corrected to bring the main frame back to its properplane. Since the support of the main frame shifts continually to adifferent set of three rams, there is extra duty put upon the controlsystem which detracts from the accuracy at which the main frame can bemaintained in the desired plane.

It is therefore one of the objects of this invention to provide a roadbuilding machine in which the grade and height of one side of the mainframe is controlled by a level guide such as a grade Wire or gradesurface and in which the cross grade of the main frame (and thereby thetool) is controlled either by a pendulum operated servo valve or bysecond level guide.

It is another object of this invention to provide a road buildingmachine having a greatly improved stability and versatility and which ismore economical to operate than those known heretofore and whichdistributes the weight of the main frame substantially equally on fourvertically adjustable supports.

It is a further object of this invention to provide a road buildingmachine having its tool-carrying main frame supported in a more equalmanner than heretofore pos sible by utilizing a three-point instead of aconventional four-point suspension system.

It is still another object of this invention to provide a road buildingmachine which includes a more practical and more reliable automaticleveling mechanism which maintains the main frame, during its advance,at a predetermined and accurately held level regardless of anyvariations in the level of the supporting traction unit and whichprovides for an equal weight distribution of the main frame upon fourvertically adjustable supports.

In accordance with a preferred embodiment of the road building machineof this invention, the vertically adjustable frame supports associatedwith the front and back of one side of the main frame are conventionallycontrolled, that is, each hydraulic ram has its own control valve whosevalve actuating member may be controlled either directly or indirectlythrough micro switches of solenoids by a control lever which engages alevel guide such as a grade Wire or a preformed slab placed along theroad. The vertically adjustable frame supports associated with the frontand back of the other side of the frame, however, have their hydraulicrams tied to a single control whose valve actuating member may either bein engagement with a second level guide placed on the other side of theroad or with a gravity operated pendulum for setting the average heightof this side of the main frame to a desired cross grade. As a result oftying the two hydraulic rams together, vertical height control along oneside of the mainframe is no longer imposed separately on the front andback supports of that side, but rather on the mid-point of that sideallowing the front and back supports to pivot about the mid-point inaccordance with the desired grade and resulting in a sharing of theload. I In other words, two valves individually control the front andrear height of one side of the main frame and a further valve controlsthe height of the mid-point between the front and rear of the other sideof the main frame. The respective heights of the front and rear of thesingle valve controlled side depending on the grade of the double valvecontrolled side of the frame. In this manner, a stable or three-pointsuspension is realized, the three points being the front and rear on oneside of the main frame and the mid-point between the front and rear onthe other side of the main frame. Since the height of one side isdetermined solely by the vertical height of its mid-point, the crossslope is now easily controlled by either a single conventional pendulumoperated servo valve or by a second level guide. Although control of themid-point is preferred, it is apparent that since, geometrically, threepoints determine a plane, any point on the other side of the main framemay be used as a control point .to establish the desired planardisposition of the main frame.

, Other objects and a fuller understanding of the.invention may be hadby reference to the following description and claims, taken inconjunction with the accompanying drawings in which:

FIGURE 1 shows a top view of the road building machine of thisinvention, certain conventional parts of the superstructure having beenomitted for the sake of clarity;

FIGURE 2 shows a side elevational view of the road building machine ofFIGURE 1;

7 .FIGURE 3 shows a side elevational view of a further embodiment of theroad building machine of this invention;

FIGURE 4 shows a schematic hydraulic flow diagram of the three-pointsuspension control system employed in the machine of this invention; and

, FIGURE 5 shows an illustrative diagram of the effective height of theside of the main frame controlled by a single control valve.

Referring now to the drawings, in which like characters designate likeparts, there is shown a main frame generally indicated as 10, having twovertically extending side frame members 12 and 14, two verticallyextending cross frame members 16 and 18 for connecting side framemembers 12 and 14 to one another, and two horizontally extending webs orribs 20 and 22 for strengthening the connection between cross framemember 16 and side frame members 12 and 14 and for providing additionalrigidity to main frame 10. 1 Suspended between and mounted to side framemembers 12 and 14 are road building tools such as striker blade 24 andthe conveyor screw 26. During operation of the road building machine ofthis invention these tools are in contact with the ground and build theroad. Of course, a large number of different road building tools may besubstituted for or added to blade 24 and screw 26, depending on theparticular workto be done. In some instances, many different tools aremounted in vertically adjustable mounts to be selectively lowered forground engagement. In the case of laying base, asphalt or concrete,appropriate hoppers are suspended on the, main frame, carrying thedesired material to be deposited upon the road bed.

Four ground traction units 30, 31, 32 and 33 associated respectivelywith the front and rear of each side of mainframe 10, serve to supportand to propel main frame'10 over the ground. The ground traction unitsmay comprise spoke wheels and 31" engaging an endless track 35 (FIG; 2)or individual wheels 36 and 37- (FIG. 3) having coarsely treaded tiresmounted thereon. Each ground traction unit is rotatably mounted upon ashort axle respectively designated as 30', 31, 32' and 33. A track frame27 supports axles 30' and 31' in spaced horizontal relationship to oneanother.

Shaft 30' is supported by a rocker bracket 40 which pivots about a shaft41 carried by a support bracket 42 mounted on a bolster 43 bolted orotherwise affixed to frame 10. The other end of rocker bracket 40 isrotatably connected to plunger 44 of a horizontally extending hydraulicram 45 connected by a bracket 46 to bolster 43. Similarly, shaft 31' isrotatably supported by'a pair of links 47 which are rotatably mountedupon a shaft 48 in the lower end of rocker bracket 49. Rocker bracket 49is pivoted about shaft 50 in bracket 51 attached to a bolster 52connected to main frame 10. The other end ;of rocker bracket 49 isrotatably connected to the plunger 53 of a horizontally extendinghydraulic ram 54 attached to bracket 55 of bolster 52., The combinationof a hydraulic ram, and associated linkages is referred toherein asvertically adjustable frame supports. The other e ses t6 side of theroad building machine is likewise provided with a spacer bar and framesupports connected in the same manner as the ones described hereinabove.

The operation of the linkage mechanism including the hydraulic rams willnow be explained. As hydraulic ram 45 gets a commandand expels plunger44, rocker bracket 40' starts turning clockwise about axle 30' (whichcannot move vertically) and raises shaft 41 bolster 43 and thereby frame10. Likewise, as plunger 53 comes out of ram 54, rocker arm 49 turnsabout shaft 48 and lifts bolster 52. Retraction of the plungers willcause a lowering of this side. of main frame 10.

The drive unit, for propelling main frame 10 in either a forward orreverse direction, may be provided by mounting a pair of engines and 60'on brackets above the track frames such as track frame 27 shown in FIG.2 and connecting engine, 60 by means of a chain drive 61 to anappropriate chain gear 62 mounted on hubs fastened to shafts 30 and 32'.Alternatively, the self-propelled traction units 30, 31, 32, 33 can bereplaced by simple wheels or other ground engagement means with no powerapplied directly thereto. Since neither this traction unit nor the frameconstruction per se constitute any part of this invention and are wellknown to those skilled in the art of road building machines, no furtherparticulars thereof are deemed necessary.

The road building machine shown in FIG. 3 differs from the one of FIG. 2in that the horizontally extend ing hydraulic rams 65 and 66 are locatedbetween the front and rear ground traction unit. Rams 65 and 66 areattached to bolsters 67 and 68, respectively, which are bolted totraction frame 69 which supports the short axles 70 and 71 in spacedhorizontal relationship. Axles 70 and 71 respectively support wheels 36and 37 and serve as pivots for a pair of rocker brackets 72 and 73.Rocker bracket 72 has one end connected to a bracket 74 mounted to abolster 75 fixed to main frame 76 and has the other end connected to aplunger 77 of hydraulic ram 65.

' Rocker bracket 73 has one end connected, via a pair of links 78, to abracket 79 mounted upon bolster 80 fixed to main frame 76 and the otherend is connected to plunger 81 of hydraulic ram 66. The other side ofthe machine of FIG. 3 is supported in like manner.

The operation of the frame support means of FIG. 3 will now beexplained. As hydraulic ram 65 receives a command to expand, rocketbracket 72 rotates about shaft 70 and lowers support bracket 74 andthereby frame 76. The same command applied to hydraulic ram 66 willlikewise cause clockwise rotation of rocker bracket 73 about shaft 71and lower bolster 80. Upon a command to retract, plungers 77 and 81 willcause a raising of frame 76. When hydraulic ram 65 is actuated, frame 76has a horizontal component of motion with respect to traction frame69-because rocker bracket 72 moves bolster 75 along an arcuate pathabout shaft 70. Toallow for such horizontal motion, an articulateconnection comprising link 78 is provided for support of the other endof spacer bar 69 through rocker bracket 73.

FIG. 4 shows four hydraulic rams in spaced relation to correspond withthe top plan view of FIG. 1, which are respectively designated byreference characters 90, 91, 92 and 93. The'hydraulic fluid system foroperating the four hydraulic rams include an oil tank for holdinghydraulic fluid, a pump 101 connected thereto to develop hydraulicpressure, and a conventional regulator valve 102 connected across tank100 and pump 101. Tank 100, pump'101' and bypass valve 102therefore'define a constant hydraulic fluid pressure system whichsupplies hydraulic fluid under constant pressure to a hydraulic line103;. If thepressure developed by pump 101 exceeds a predeterminedpressure, regulator valve 102 opens a by passport permitting. fluid tocirculate back to tank 100 through-bypass line 104.

Hydraulic pressure line .103 is connected to the input port-of hydrauliccontrol valves 110, 111, 112 and pendulum valve 113. Valves 110, 1-11,112 and 113 may be of the three-way closed-center type in which acentral plunger communicates the center port either with the highpressure input port or with the low pressure output port. The centerport therefore permits flow in either direction, high pressure from thehigh pressure input port to the center port when the plunger is in oneof its two positions, and low pressure flows from the center port to thelow pressure output port for the plunger in the other of its twopositions. Since the particular valve does not form any part of thisinvention and is of a conventional design, no further descriptionthereof is deemed necessary.

As stated, high pressure line 163 is connected to the high pressureinput ports of control valves 110, 111 and 112 and also to the highpressure input port of a pendulum valve 113. The center ports of controlvalves 114) and 111 are connected respectively to hydraulic rams 90 and91. Since the hydraulic rams are extended by the insertion of hydraulicfluid under high pressure and are retracted by the removal of hydraulicfluid under low pressure, a low pressure return line 105 is connectedbetween the low pressure output ports of control valves 110 and 111 andhydraulic fluid tank 109.

The center ports of control valve 112 and of pendulum valve 113 areconnected to the two input ports of a conventional three-way selectorvalve 114 which has a single output port and which may be manuallyoperated. The output port of selector valve 114 is connected to bothhydraulic rams 92 and 93. In this manner, selector valve 114 controlswhether the center port of control valve 112 or of pendulum valve 113communicates with hydraulic rams 92 and 93. Return line 105 is alsoconnected to the low pressure output port of valves 112 and 113.

Valves 110, 111, and 112 are actuated by control levers 120, 121 and122, respectively, which are connected either directly or indirectly tothe center plungers of the valves in a manner wellknown to those skilledin the art. By way of example, control levers 121), 121 and 122 may bein engagement with grade wires 125 and 126 (or grade surfaces such asprefabricated slabs) accurately set to a predetermined relation to thegrade on each side of the road and supported at intervals from theground by stakes or braclrets (see FIG. 1). As the machine advances andthe grade wire or grade surface along the side of the road rises withrespect to the main frame and therefore with respect to the roadbuilding tool, the levers are raised, causing a motion of the plunger toconnect the center port with the high pressure line and the resultantinjection of high pressure hydraulic fluid from line 103 for expandingthe hydraulic rams and thereby raising the frame and with it the blade24 or screw 26.

The height of the side associated with hydraulic rams 92 and 93 iscontrolled by single control valve 112, by means of lever 122. Ifcontrol lever 122 is in engagement with a lever control means such asgrade wire 126, it will cause the average height of that side of themain frame to correspond to the height of grade wire 126. FIG. 5 is anillustration of the result obtained by tying hydraulic rams 92 and 93 tosingle control valve 122. The points of suspension of a main frame 129are designated as 130 and 131 and correspond respectively to shafts 41and 50 of FIG. 2 consequently, the frame 132 is effectively suspended atits midpoint on the side of points 131) and 131. Since these points 130and 131 are maintained longitudinally at the same level because of theoperation of the hydraulic rams on the opposite side of the frame, themidpoint between the suspension points 130 and 131 is at this same levelindicated at 132. If now the traction means move upwardly or downwardlyas indicated at 133 and 134 in FIG. 5, a pressure differential willexist between the supporting hydraulic rams 92 and 93 which willautomatically be balanced by flow of hydraulic fluid from one ram to theother and no change in the elevation of the midpoint 13-2 will heexperienced. However, if a sensing unit such as wire 126 or the pendulumvalve senses that the point 132 moves either above or below the desiredlevel, the rams will be actuated to restore the point 132 to the desiredlevel. Together with the height and grade control of the front and rearof the other side of frame 129, the plane of the main frame and therebythe tool is positively controlled.

An important advantage realized with the control system of thisinvention, in addition to increased stability, is that the cross grademay be set by either a single pendulum or template surface operatedvalve. Pendulum valves are valves actuated by a pendulum which alwaysassumes a vertical position because of gravity forces acting thereon.The valve is set in such a way that the pendulum closes the valve for apredetermined angular position of the valve body (the cross grade) andopens the valve when the valve body angle differs from thatpredetermined angular position by either causing the injection ofhydraulic fluid at high pressure to the center port, or by permittingreturn of hydraulic pressure to the low pressure output port. Such apendulum valve is fully described in U.S. Patent No. 2,934,078 entitledPendulum Controlled Valve.

By way of summary, the road building machine of this invention may havethe height of its tool carrying main frame adjusted in a number of wayswhich will now be stated. The side of the main frame whose front andback are individually controlled by valves may have their valvesactuated either by a lever connected to the valve actuating mechanism inengagement with thehorizontally strung grade wire along the side of theroad or by a gauge Wheel connected to the valve actuating mechanismsandrunning on a preformed slab laid along the side of the road. In caseof multiple lane roads, a grade wire is strung first to provide for theproper level of the first lane. Thereafter, the first lane provides thegrade level means and the valve actuating mechanism is actuated by agauge wheel engaging the first lane surface.

The other side of the tool carrying main frame, with its single valvewhich determines the height of the midpoint of that side, provides crossgrade control. Cross grade control may be obtained in three ways: oneway comprising the valve actuating lever to be in engagement with thewire strung :along the other side of the road, a second way comprisingthe utilization of a gauge wheel connected to the valve actuatingmechanism running on a preformed slab along that side of the road, andthe third way comprising the use of a gravity operated pendulum valve asexplained hereinabove.

Any method of controlling the height of one side may be combined withany method for control of the other side of the main frame with equallygood results. For example, one side may be controlled by means of gaugewheels engaging a preformed slab while the other side may be controlledby a lever engaging a grade wire, or the height of the main frame may-becontrolled with grade wires running along both sides of the road, thesegrade Wires being in engagement with levers for con-v trolling thevalves.

Of course, the position of the lever engaging the wire or the gaugewheel engaging the preformed slab determines the height adjustmentprovided by the particular hydraulic ram with which the valve actuatingmechanism is associated. For example, in FIG. 4, lever 122 actuatingvalve 112 is positioned a considerable distance away from the midpointwhich it controls. In such a case, the midpoint is set to correspond tothe level means at that position. It is usually desirable to have thecontrol lever engage the level means as close as possible to the position of the vertically adjustable frame supports it controls, so thatthe grade means may be set more easily to provide a corresponding heightwhere placed at the point of sponse.

7 its location; Placing the actuating lever, such as lever 122 of FIG.4, ahead of the road building machine may be used in certain-instancesto overcome a lack of re- But ordinarily the lack of response is soshort that such a lead time will not be necessary. Actuating lever 122,as shown in FIG. 1, is placed in the middle of the road buildingmachine, a position better suited than the position indicated in FIG. 4.

There has been described a novel road building machine in which the toolcarrying main frame is provided with a three point suspension forgreater stability and versatility of operation and in which the weightof the main frame is equally distributed on four frame supports. Twosuspension points are the front and back of one side of the main frameand the third suspension point is the midpoint between the physicalsuspension points of the other side of the main frame. Such a supportsystem makes it possible to control the plane of the main frame 'with asingle level means and a single pendulum valve.

What is claimed is:

1. A road building machine comprising: a rectangular main frame; atleast one working tool for road engagement supported by said frame;front and rear ground traction means on opposite sides of said mainframe; frame support means connecting each of said ground traction meansto said main frame, said frame support means including hydraulicallyoperated rams for providing vertical adjustment of said main frame withrespect to each of said ground traction means; three normally closedhydraulic ram actuating means, two of said actu ating meansindependently operating the rams associated with the front and reartraction units on one side of said main frame and the remainingactuating means collectively operating the rams associated with thefront and rear traction units of the other side of said main frame; thehydraulic rams on the other side of said frame being interconnected by acommon conduit; level control means on said machine operating each'ofsaid actuating means, the level control means for said two actuatingmeans on said one side of the main frame being spaced longitudinally toengage common grade means, and the level control for the remainingactuating means being adapted to engage separate grade means, said grademeans and separate grade means being disposed along the road on oppositesides of said machine.

2. A road building machine comprising: a rectangular main frame; atleast one working tool for road engagement supported by said frame; fourground traction means for propelling said road building machine; fourframe support means connecting said ground traction means to front andrear of opposite sides of said main frame; said 'frame support meansincluding hydraulic rams for pro- 'viding vertical adjustment of thefour corners of said main frame with respect to ground traction means;separate valves connected to each of the hydraulic rams associated withthe front and rear of one side of said main frame; a common conduitinterconnecting the hydraulic rams associated with the front and rear ofthe other side of said main frame; a valve connected to said commonconduit to control fluid pressure therethrough to said rams;longitudinally-spaced level control means on said machine adapted toengage grade means along one side of said road building machine, saidlevel control means engaging and operating said separate valves; and agravity'operated means engaging and operating said common valve.

3. A road building machine comprising: a main frame; at least oneworking tool for road engagement supported by said frame; front and rearground traction means on theopposite sides of said frame; frame supportmeans Zvalves, two of said valves being connected to independentlyoperate the hydraulic rams associated with the two ground traction meanson one side of said main frame, the hydraulic rams on the other side ofsaid frame being directly connected through a common conduit, and theremaining valve being connected through said'common conduit tocollectively operate the hydraulic rams associated with the other sideof said main frame; a hydraulic fluid pressure system connected to saidthree valves; and longitudinally spaced grade level control means on oneside of said main frame for actuating said two valves to operate saidrams and thereby change the height of one side of said main frame upondeviation of the road surface traversed from a predetermined grade, andlevel control means on the other side of the main frame for actuatingsaid remaining valve thereby to change the height of the side of saidmain frame upon deviation of the'road surface traversed from apredetermined cross-grade. p

4. A road building machine comprising: a rectangular main frame; atleast one working tool for road engagement supported by said frame; fourground traction means; four frame support means connecting said groundtraction means to the front and rear of both sides of said main frame,said frame support means including hydraulically operated rams forproviding vertical adjustment of the four corners of said main framewith respect to said ground traction means; three normally closedvalves, two of said valves being connected to independently operate thehydraulic rams associated with the front and back frame support meansalong one side of said main frame, the hydraulic rams on the other sideof'said frame being connected through a common conduit, and theremaining valve being connected through said common conduit tocollectively operate the hydraulic rams associated with the supportmeans along the other side of said main frame; a hydraulic fluidpressure system connected to said three valves; and grade and crossgrade level control means operatively associated with said two'valvesand said remaining valve, respectively to operate said rams upondeviation of the road surface traversed from a predetermined grade andcross grade of said main frame.

5. Support and level control mechanism for a road building machine whichincludes a tool holding rectangular main frame and ground traction unitsin front and rear of each side of said main frame, said support andlevel control mechanism comprising: vertically adjustable frame supportsincluding hydraulic rams connecting said main frame to said groundtraction units; first, second and third normally closed control valves;a hydraulic fluid pressure and return system connected to said controlvalves, said first and second control valves being respectivelyconnectedto the hydraulic rams associated with the front andthe rear ofone side of said main frame,'the hydraulic rams on the other side ofsaid frame being interconnected by a commonconduit, said third controlvalve being connected through said common conduit to both hydraulic ramsassociated with the other side of said main frame; a three-way selectorvalve interposed between said third control valve and the ramsassociated therewith; a pendulum-controlled valve mounted to said mainframe and connected between said pressure and return system and saidselector valve selectively communicating said third and said pendulumvalve with its associated hydraulic rams, said pendulum-controlled valvebeing gravity operated to raise and lower said other side of said mainframe upon deviation of the road traversed by said road building machinefrom a predetermined cross grade; and a pair of spaced level controlmeans on one side of said machine for engaging a common grade indicatordisposed along the road traversed by the machine for actuatingsaid'first and second valves for level adjustment of said main frame inaccordance with the level *of said grade indicator.

6. A road building machine in accordance with claim 5 in which the framesupports include a rocker bracket pivotally mounted to said main frameand in which the hydraulic ram is horizontally disposed and connected atopposite ends to said main frame and to one end of said rocker bracket,the other end of said rocker bracket being coupled to the groundtraction means.

7. A road building machine comprising a frame, a working tool carriedthereby, a pair of ground engagement means disposed adjacent oppositesides of said frame, first and second frame support means connectingopposite sides of said frame to respective ground engagement means foradj-ustably supporting said frame thereon in a desired plane, said firstframe support means including two vertically adjustable supportsconnected to said frame at spaced positions so as to define two pointsof support, actuating means for said first frame support means andadapted for operative engagement with an exterior grade controlreference disposed along the path to be traversed by said road buildingmachine, said second frame support means including two hydraulic ramsconnected to said frame at longitudinally-spaced positions andhydraulically interconnected by a common conduit, a valve connectedthrough said conduit to both of said rams for controlling the supply ofhydraulic fluid thereto wherefore identical hydraulic pressure exists insaid rams; and means operative in response to a variation in elevationof the side of said frame supported by said second frame support meansfor simultaneously actuating said hydraulic rams.

References Cited by the Examiner UNITED STATES PATENTS 2,844,882 7/ 1958Early.

2,864,452 12/1958 Guntert.

2,883,594 4/1959 Alberts 318l9 3,029,715 4/1962 Bowen 94-46 OTHERREFERENCES Woll: German printed application No. 1,010,980, 6/57.

CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, Examiner.

3. A ROAD BUILDING MACHINE COMPRISING: A MAIN FRAME; AT LEAST ONEWORKING TOOL FOR ROAD ENGAGEMENT SUPPORTED BY SAID FRAME; FRONT AND REARGROUND TRACTION MEANS ON THE OPPOSITE SIDES OF SAID FRAME; FRAME SUPPORTMEANS CONNECTING SAID MAIN FRAME TO EACH OF SAID GROUND TRACTION MEANSSAID FRAME SUPPORT MEANS INCLUDING HYDRAULICALLY OPERATED RAMS FORVERTICALLY ADJUSTING SAID MAIN FRAME WITH RESPECT TO EACH OF SAID GROUNDTRACTION MEANS; THREE VALVES, TWO OF SAID VALVES BEING CONNECTED TOINDEPENDENTLY OPERATE THE HYDRAULIC RAMS ASSOCIATED WITH THE TWO GROUNDTRACTION MEANS ON ONE SIDE OF SAID MAIN FRAME, THE HYDRAULIC RAMS ON THEOTHER SIDE OF SAID FRAME BEING DIRECTLY CONNECTED THROUGH A COMMONCONDUIT, AND THE REMAINING VALVE BEING CONNECTED THROUGH SAID COMMONCONDUIT TO COLLECTIVELY OPERATE THE HYDRAULIC RAMS ASSOCIATED WITH THEOTHER SIDE OF SAID MAIN FRAME; A HYDRAULIC FLUID PRESSURE SYSTEMCONNECTED TO SAID THREE VALVES; AND LONGITUDINALLY SPACED GRADE LEVELCONTROL MEANS ON ONE SIDE OF SAID MAIN FRAME FOR ACTUATING SAID TWOVALVES TO OPERATE SAID RAMS AND TEHREBY CHANGE THE HEIGHT OF ONE SIDE OFSAID MAIN FRAME UPON DEVIATION OF THE ROAD SURFACE TRAVERSED FROM APREDETERMINED GRADE, AND LEVEL CONTROL MEANS ON THE OTHER SIDE OF THEMAIN FRAME FOR ACTUATING SAID REMAINING VALVE THEREBY TO CHANGE THEHEIGHT OF THE SIDE OF SAID MAIN FRAME UPON DEVIATION OF THE ROAD SURFACETRAVERSED FROM A PREDETERMINED CROSS-GRADE.